1. Technical Field of the Invention
The present invention relates to an electro-optic device having an electro-optic substance held between a pair of substrates, and an electronic apparatus employing the electro-optic device. More specifically, the present invention relates to the structure of electrodes and terminals in each of the substrates constituting the electro-optic device.
2. Description of the Related Art
Of various types of electro-optic devices, one (liquid crystal device) utilizing a liquid crystal as an electro-optic substance comprises, as shown in FIG. 21, a first transparent substrate 10Z and a second transparent substrate 20Z arranged in an opposed relation, a sealing material 30 for bonding both the substrates to each other, and a liquid crystal sealed in an area surrounded by the first transparent substrate 10Z, the second transparent substrate 20Z and the sealing material 30. In a state of the first transparent substrate 10Z and the second transparent substrate 20Z being bonded to each other in an opposed relation, the first transparent substrate 10Z has a portion 25′ extending out of an edge of the second transparent substrate 20Z, and the second transparent substrate 20Z has a portion 25″ extending out of an edge of the first transparent substrate 10Z.
A plurality of first electrodes 40Z are formed on a surface of the first transparent substrate 10Z opposing to the second transparent substrate 20Z. The first electrodes 40Z are formed to extend up to the extended portion 25′ of the first transparent substrate 10Z for connection to a driving IC 7Z′ mounted in the extended portion 25′. On the other hand, a plurality of second electrodes 50Z are formed on a surface of the second transparent substrate 20Z opposing to the first transparent substrate 10Z in a crossed relation to the first electrodes 40Z. The second electrodes 50Z are formed to extend up to the extended portion 25″ of the second transparent substrate 20Z for connection to a driving IC 7Z″ mounted in the extended portion 25″. Thus, output signals from the driving IC 7Z′ are supplied to the first electrodes 40Z, and output signals from the driving IC 7Z″ are supplied to the second electrodes 50Z.
However, such a construction has the problem that the size of the electro-optic device is increased because the first transparent substrate 10Z and the second transparent substrate 20Z have the extended portions 25′, 25″.
To overcome the above problem, there has been proposed an electro-optic device of the type that permits signals to be inputted from one substrate to the other substrate by utilizing electrical conduction between both the substrates. This electrical conduction between both the substrates is established as shown in FIGS. 22 and 23. When a first transparent substrate 10Z and a second transparent substrate 20Z are bonded to each other, inter-substrate conducting terminal portions 60Z constituted by ends of the first electrodes 40Z formed on the first transparent substrate 10Z and end portions 70Z of terminals formed on the second transparent substrate 20Z are placed in an opposed relation. In this condition, the sealing material 30 is hardened while applying forces to narrow a gap between the inter-substrate conducting terminal portions 60Z and the terminal end portions 70Z so that conductive particles 31 dispersed in the sealing material 30 are collapsed between the first transparent substrate 10Z and the second transparent substrate 20Z. As a result, the conductive particles 31 present between the inter-substrate conducting terminal portions 60Z and the terminal end portions 70Z establish electrical conduction between them, while the other conductive particles 31 present in other areas than the areas, in which the inter-substrate conducting terminal portions 60Z and the terminal end portions 70Z are opposed to each other, are not collapsed and do not take part in the electrical conduction between them. Therefore, only the inter-substrate conducting terminal portions 60Z and the terminal end portions 70Z are electrically conducted to each other.
As described below in connection with FIG. 23, the size of the electro-optic device can be reduced by utilizing the electrical conduction thus established between both the substrates. Referring to FIG. 23, the second transparent substrate 20Z is formed to be greater than the first transparent substrate 10Z, and the second transparent substrate 20Z has a portion 25Z extending out of an edge of the first transparent substrate 10Z. In the extended portion 25Z, a driving IC 7 is mounted for supplying predetermined signals to first electrodes 40Z of the first transparent substrate 10Z and second electrodes 50Z of the second transparent substrate 20Z. By utilizing the electrical conduction, described above with reference to FIG. 22, in a region circumscribed by a circle C in FIG. 23, output terminals of the driving IC 7Z mounted on the second transparent substrate 20Z are connected to the first electrodes 40Z of the first transparent substrate 10Z as well through the electrical conduction between both the substrates.
Employing such a construction reduces the size of the electro-optic device as compared with the electro-optic device shown in FIG. 21 because only the one extended portion 25′ is needed.
Further, even in an electro-optic device not employing the COG mounting, it is only necessary to connect a flexible board to one extended portion as shown in FIGS. 24 to 29.
FIGS. 24 and 25 are respectively a perspective view and an exploded perspective view of a conventional electro-optic device. FIG. 26 is a sectional view of one end of the electro-optic device on the side indicated by XIV′ when sectioned along line XIV-XIV′ in FIG. 24. FIG. 27 is a plan view showing, in enlarged scale, electrodes and terminals formed on a first transparent substrate of the electro-optic device shown in FIGS. 24, 25 and 26, and FIG. 28 is a plan view showing, in enlarged scale, electrodes and terminals formed on a second transparent substrate of the electro-optic device shown in FIG. 25. FIG. 29 is a plan view showing, in enlarged scale, the electrodes and the terminals in a state where the first transparent substrate shown in FIG. 27 and the second transparent substrate shown in FIG. 28 are bonded to each other.
The electro-optic device shown in those drawings is also a liquid crystal device of passive matrix type. As schematically shown in FIGS. 24, 25 and 26, a pair of substrates each being made of a rectangular glass, for example, are bonded to each other by a sealing material 30 with a predetermined gap left therebetween, and a liquid crystal sealed-in space 35 is defined by the sealing material 30 between both the substrates. A liquid crystal as an electro-optic substance is sealed in the liquid crystal sealed-in space 35 to form a liquid crystal layer 4 (electro-optic layer), and an inner area of the liquid crystal sealed-in space 35 serves as an image display area 2. In this description, of the pair of substrates, one provided with first electrodes 40X (pixel addressing electrodes) including drive portions 41X formed thereon to extend over the image display area 2 in the direction of length is assumed to be a first transparent substrate 10X, and the other provided with second electrodes 50Y (pixel addressing electrodes) including drive portions 51Y formed thereon to extend over the image display area 2 in the direction of width is assumed to be a second transparent substrate 20Y.
On the second transparent substrate 20Y, as shown in FIG. 26, sets of color filters 7R, 7G and 7B of red (R), green (G) and blue (B) are formed in areas corresponding to points at which the first electrodes 40X intersect the second electrodes 50Y. An insulating flattening film 21, the second electrodes 50Y and an alignment film 22 are formed in this order on the surface side of the color filters 7R, 7G and 7B. In the first transparent substrate 10X, an alignment film 12 is formed on the surface side of the first electrodes 40X.
This electro-optic device 1X is of the transmissive type, and the first electrodes 40X and the second electrodes 50Y are each formed of an ITO film (Indium Tin Oxide/transparent conductive film). In the electro-optic device 1X, a polarizing plate 62 is affixed to an outer surface of the second transparent substrate 20Y, and a polarizing plate 61 is affixed to an outer surface of the first transparent substrate 10X. Further, a backlight device 9 is disposed outside the first transparent substrate 10X.
In the transmissive electro-optic device 1X having the above-described construction, the light emitted from the backlight device 9 enters the first transparent substrate 10X and then exits from the side of the second transparent substrate 20Y after being modulated by the liquid crystal layer 4.
In the electro-optic device 1X, as shown in FIGS. 24 and 25, inputting of signals from the exterior and electrical conduction between both the substrates are made using areas near respective one sides 101X, 201Y of the first transparent substrate 10X and the second transparent substrate 20Y, which are located in the same direction. To this end, a portion of the first transparent substrate 10X near the side 101X thereof is extended out of an edge of the second transparent substrate 20Y to form an extended portion 15X, and a flexible board 90 including a driving IC 7X mounted thereon is connected to the extended portion 15X. Also, an area of the first transparent substrate 10X, on which the side 201Y of the second transparent substrate 20Y lies, is used to establish the electrical conduction with the second transparent substrate 20Y.
To realize such a construction, as shown in FIGS. 25 and 27, a plurality of first terminals 81X are formed in opposite outer areas of the first transparent substrate 10X in the longitudinal direction of the side 101X thereof, and a plurality of second terminals 82X are formed in a central area of the first transparent substrate 10X in the same longitudinal direction.
In the first transparent substrate 10X, the second terminals 82X are constituted by ends of the first electrodes 40X. The first electrodes 40X comprise wiring portions 42X extending straight from the second terminals 82X toward a side 102X of the first transparent substrate 10X opposing to the side 10X (i.e., toward the image display area 2) and then extending obliquely outward, and drive portions 41X extending straight from the wiring portions 42X toward the opposing side 102X of the first transparent substrate 10X. Herein, the first electrodes 40X and the first terminals 81X are formed of an ITO film.
On the other hand, as shown in FIGS. 25 and 28, the second electrodes 50Y formed on the second transparent substrate 20Y comprise drive portions 51Y, wiring portions 52Y leading from the drive portions 51Y, and inter-substrate conducting terminal portions 70Y formed at ends of the wiring portions 52Y. The inter-substrate conducting terminal portions 70Y are formed to lie side by side along the side 201Y of the second transparent substrate 20Y. Herein, the second electrodes 50X are formed of an ITO film.
On the second transparent substrate 20Y, the wiring portions 52Y are routed so as to bypass an area overlapping the wiring portions 42X of the first electrodes 40X formed on the first transparent substrate 10X when viewed from above, passing through areas located on both sides of that overlapping area. Therefore, the inter-substrate conducting terminal portions 70Y are shaped such that they are linearly formed in a central region of the side 201Y of the second transparent substrate 20Y, but a proportion of an obliquely extending zone (inclined zone 702Y) in each entire terminal portion 70Y is increased as they extend toward the left and right farther away from the central region of the side 210Y.
Unlike the normal wiring portions, the inter-substrate conducting terminal portions 70Y establish the electrical conduction with ends 60X of the second terminal 82X through conductive particles held between both the substrates, and are hence more likely to cause a short-circuiting between the adjacent terminals. To surely prevent a short-circuiting between those terminals, it is necessary to secure a sufficiently wide spacing between the adjacent terminals. For this reason, those of the inter-substrate conducting terminal portions 70Y, which are located close to the opposite ends of the side 201Y of the second transparent substrate 20Y, are formed to have straight zones 701Y with lengths differing to a relatively large extent between the adjacent terminal portions 70Y, so that a relatively wide spacing is ensured between the adjacent inclined zones 702Y obliquely extending from the straight zones 701Y. Therefore, an angle α formed by a line E connecting the boundaries of the straight zones 701Y and the inclined zones 702Y of the inter-substrate conducting terminal portions 70Y with respect to the side 201Y of the second transparent substrate 20Y is fairly large.
On the other hand, those of the inter-substrate conducting terminal portions 70Y, which are located in a region closer to the center of the side 201Y of the second transparent substrate 20Y, are extended straight thoroughly. Zones obliquely extending from ends of the inter-substrate conducting terminal portions 70Y constitute the wiring portions 52Y that do not take part in establishing the electrical conduction between both the substrates through conductive particles. In the wiring portions 52Y, therefore, the spacing between adjacent patterns can be fairly narrowed. Thus, in the region closer to the center of the side 201Y of the second transparent substrate 50Y, an angle formed by a line connecting the boundaries between straight zones 501Y and inclined zones 502Y of the inter-substrate conducting terminal portions 70Y with respect to the side 201Y of the second transparent substrate 20Y is fairly small.
When constructing the electro-optic device 1X using the first transparent substrate 10X and the second transparent substrate 20Y which have the above-described construction, in the step of bonding the first transparent substrate 10X and the second transparent substrate 20Y through a sealing material 30 as shown in FIGS. 25 and 29, a gap material and conductive particles are mixed in the sealing material 30, and the sealing material 30 is further applied to an area in which the ends 60X of the first terminals 81X and the inter-substrate conducting terminal portions 70Y are positioned to lie one above the other. By bonding the first transparent substrate 10X and the second transparent substrate 20Y through the sealing material 30, therefore, the ends 60X of the first terminals 81X and the inter-substrate conducting terminal portions 70Y are electrically conducted with each other through the conductive particles. Also, as a result of bonding the first transparent substrate 10X and the second transparent substrate 20Y, pixels 5 are formed in a matrix pattern by points at which the drive portions 41X of the first electrodes 40X intersect the drive portions 51Y of the second electrodes 50Y.
Accordingly, by mounting the flexible board 90 to the first terminals 81X and the second terminals 82X, which are formed on the first transparent substrate 10X along the side 101X thereof, with the aid of an anisotropic conductive material or the like, and then inputting signals to the first terminals 81X and the second terminals 82X through the flexible board 90, image data signals can be directly applied from the second terminals 82X to the first electrodes 40X formed on the first transparent substrate 10X, and scan signals can be applied to the second electrodes 50Y formed on the second transparent substrate 20Y through the first terminals 81X, the conductive particles and the inter-substrate conducting terminal portions 70Y.
However, since the electrical conduction between both the substrates is conventionally established using the inter-substrate conducting terminal portions 70Y having the obliquely extending zones, there arises a problem that a sufficient spacing between the inclined zones 702Y of the adjacent terminal portions 70Y must be ensured by forming the straight zones 701Y to have lengths differing from each other to a relatively large extent, thus resulting in wasteful use of an area that is positioned outside the image display area 2 and includes the inter-substrate conducting terminal portions 70Y. In the conventional electrode structure, if the number of the second electrodes 50Y is further increased in a region (having a region width indicated by arrow B) where patterns must be obliquely formed between a corner portion of an innermost one of the first electrodes 40X formed on the first transparent substrate 10X, which is bent near a corresponding corner of the image display area 2, and a base end portion of an outermost one of the first terminals 81X, the wiring portions 52Y of the second electrodes 50Y are overlapped with the wiring portions 42X of the first electrodes 40X in an area 250 shown in FIG. 29. This results in a higher probability that a short-circuiting may occur between both the substrates. Also, if the spacing between the inclined zones 702Y of the inter-substrate conducting terminal portions 70Y is narrowed to create an area allowing addition of the second electrodes 50Y with the view of increasing the number of the second electrodes 50Y, this try increases a probability that a short-circuiting may occur between the adjacent terminals. Further, if a solution of reducing, e.g., the line width of the inter-substrate conducting terminal portion 70Y and/or the wiring portion 52Y of each second electrode 50Y is tried to forcibly create such an area allowing addition of the second electrodes 50Y by narrowing the region width B, electrical resistance in those portions is increased and therefore display quality deteriorates.
In view of the above-described problems, an object of the present invention is to provide an electro-optic device of a type that permits signals inputted through external input terminals formed on one substrate to be inputted to the other substrate through electrical conduction between both the substrates, the device being constructed to be able to increase the number of electrodes through proper design of a wiring structure and wire material without deteriorating reliability and display quality.
Another object of the present invention is to provide an electro-optic device in which restrictions upon materials of conductive films constituting electrodes are alleviated without deteriorating display quality based on combination of the principles of both the transmissive type and the reflective type.
Still another object of the present invention is to provide an electronic apparatus employing such an electro-optic device.